Maeda Seisakusho Co., Ltd.

Eiji Ichimura

Ryosuke Nakamura

Shinya Tokutome

Mitsuaki Wada

Tatsufumi Tomura

Masakazu Midorikawa

Nozomu Toufukuji

A crawler crane includes: a seating switch that detects whether an operator is in a driver seat; a turn angle potentiometer that detects the turn position of a boom; and a controller. The controller is provided with a boom turn restriction control unit for performing a boom turn-restricting control whereby the boom is not allowed to turn within a predetermined angular range above the driver seat on the basis of the output from the turn angle potentiometer. The boom turn restriction control unit includes a restriction-canceling unit that cancels the boom turn-restricting control performed by a turn-restricting unit if a preset restriction-canceling condition is met. The boom turn restriction control unit cancels the boom turn-restricting control if the seating switch does not detect an operator. Ease of operation and work can thus be improved in a remote operation mode and the like.

Mobile crane

A safety device for a mobile crane has: a permitted work range setting unit that, in accordance with whether or not the overhang angle of each outrigger is a reference overhang angle and the overhang length is the maximum overhang length, sets the permitted work range/non-permitted work range of a crane boom; and a load-specific work range setting unit that, in accordance with whether or not each of the outriggers overhang lengths is a maximum overhang length, sets a maximum RTL work range which is a range, within the permitted work range, in which crane work at a maximum rated total load can be carried out. The crane work capacity on the side of the outrigger having the maximum hangover length with high supporting capacity can be fully utilized within a range over which safety can be ensured.

Safety device for mobile crane

In a crawler crane, while a fly jib is in use, the fly jib is suspended from a coupling flange by a jib raising/lowering wire rope that is wound around a sheave, the sheave being slidably attached to a tip end side section of the fly jib. If the sheave is caused to slide by a jib raising/lowering cylinder attached to the fly jib, the fly jib suspended from the coupling flange by the jib raising/lowering wire rope inclines with respect to a boom. The raising/lowering mechanism of the fly jib is installed on the fly jib side, thus making it possible to easily perform work to extract/store the fly jib.

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Nagano, Japan

Eiji Ichimura